Cable-type secondary battery

ABSTRACT

Disclosed herein is a cable-type secondary battery having a horizontal cross section of a predetermined shape and extending longitudinally, comprising: a core for supplying lithium ions, which comprises an electrolyte; an inner electrode, comprising an open-structured inner current collector surrounding the outer surface of the core for supplying lithium ions, an inner electrode active material layer formed on the surface of the inner current collector, and a first electrolyte-absorbing layer formed on the outer surface of the inner electrode active material layer; a separation layer surrounding the outer surface of the inner electrode to prevent a short circuit between electrodes; a second electrolyte-absorbing layer formed on the surface of the separator; and an outer electrode surrounding the outer surface of the second electrolyte-absorbing layer and comprising an outer electrode active material layer and an outer current collector.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/KR2012/008400 filed on Oct. 15, 2012, which claims priority under 35USC 119(a) to Korean Patent Application No. 10-2011-0104874 filed in theRepublic of Korea on Oct. 13, 2011 and Korean Patent Application No.10-2012-0114109 filed in the Republic of Korea on Oct. 15, 2012, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a cable-type secondary battery, whichcan freely change in shape, and more particularly to a cable-typesecondary battery having a core for supplying lithium ions.

BACKGROUND ART

Secondary batteries are devices capable of storing energy in chemicalform and of converting into electrical energy to generate electricitywhen needed. The secondary batteries are also referred to asrechargeable batteries because they can be recharged repeatedly. Commonsecondary batteries include lead accumulators, NiCd batteries, NiMHaccumulators, Li-ion batteries, Li-ion polymer batteries, and the like.When compared with disposable primary batteries, not only are thesecondary batteries more economically efficient, they are also moreenvironmentally friendly.

Secondary batteries are currently used in applications requiring lowelectric power, for example, equipment to start vehicles, mobiledevices, tools, uninterruptible power supplies, and the like. Recently,as the development of wireless communication technologies has beenleading to the popularization of mobile devices and even to themobilization of many kinds of conventional devices, the demand forsecondary batteries has been dramatically increasing. Secondarybatteries are also used in environmentally friendly next-generationvehicles such as hybrid vehicles and electric vehicles to reduce thecosts and weight and to increase the service life of the vehicles.

Generally, secondary batteries have a cylindrical, prismatic, or pouchshape. This is associated with a fabrication process of the secondarybatteries in which an electrode assembly composed of an anode, acathode, and a separator is mounted in a cylindrical or prismatic metalcasing or a pouch-shaped casing of an aluminum laminate sheet, and inwhich the casing is filled with electrolyte. Because a predeterminedmounting space for the electrode assembly is necessary in this process,the cylindrical, prismatic or pouch shape of the secondary batteries isa limitation in developing various shapes of mobile devices.Accordingly, there is a need for secondary batteries of a new structurethat are easily adaptable in shape.

To fulfill this need, suggestions have been made to develop linearbatteries having a very high ratio of length to cross-sectionaldiameter. Korean Patent Application publication No. 2005-99903 disclosesa flexible battery consisting of an inner electrode, an outer electrodeand an electrolyte layer interposed therebetween. However, such batteryhas poor flexibility. The linear batteries use a polymer electrolyte toform an electrolyte layer, but this causes difficulties in the inflow ofthe electrolyte into an electrode active material, thereby increasingthe resistance of the batteries and deteriorating the capacity and cyclecharacteristics thereof.

DISCLOSURE Technical Problem

The present invention is designed to solve the problems of the priorart, and therefore it is an object of the present invention to provide asecondary battery having a new linear structure, which can easily changein shape, maintain excellent stability and performances as a secondarybattery, and facilitate the inflow of an electrolyte into an electrodeactive material.

Technical Solution

In order to achieve the objects, the present invention provides acable-type secondary battery having a horizontal cross section of apredetermined shape and extending longitudinally, comprising: a core forsupplying lithium ions, which comprises an electrolyte; an innerelectrode, comprising an open-structured inner current collectorsurrounding the outer surface of the core for supplying lithium ions, aninner electrode active material layer formed on the surface of the innercurrent collector, and a first electrolyte-absorbing layer formed on theouter surface of the inner electrode active material layer; a separationlayer surrounding the outer surface of the inner electrode to prevent ashort circuit between electrodes; a second electrolyte-absorbing layerformed on the surface of the separator; and an outer electrodesurrounding the outer surface of the second electrolyte-absorbing layerand comprising an outer electrode active material layer and an outercurrent collector.

The open-structured inner current collector is preferably in the form ofa wound wire or a mesh, but is not particularly limited thereto.

In the outer electrode, the outer electrode active material layer may beformed to surround the outer surface of the second electrolyte-absorbinglayer, and the outer current collector may be formed to surround theouter surface of the outer electrode active material layer; the outercurrent collector may be formed to surround the outer surface of thesecond electrolyte-absorbing layer, and the outer electrode activematerial layer may be formed to surround the outer surface of the outercurrent collector; the outer current collector may be formed to surroundthe outer surface of the second electrolyte-absorbing layer, and theouter electrode active material layer may be formed to surround theouter surface of the outer current collector and come into contact withthe second electrolyte-absorbing layer; or the outer electrode activematerial layer may be formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer current collector may beformed to be included inside the outer electrode active material layerby being covered therein and to surround the outer surface of the secondelectrolyte-absorbing layer with spacing apart therefrom.

In the present invention, the outer current collector is notparticularly limited to its forms, but is preferably in the form of apipe, a wound wire, a wound sheet or a mesh.

The inner current collector is not particularly limited to its kinds,but is made of stainless steel, aluminum, nickel, titanium, sinteredcarbon, or copper; stainless steel treated with carbon, nickel, titaniumor silver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; or a conductive polymer.

Examples of the conductive material which may be used in the presentinvention include polyacetylene, polyaniline, polypyrrole,polythiophene, polysulfurnitride, indium tin oxide (ITO), silver,palladium, nickel, and mixtures thereof. The conductive polymer may beselected from the group consisting of polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, and mixtures thereof.

The outer current collector may be made of stainless steel, aluminum,nickel, titanium, sintered carbon, or copper; stainless steel treatedwith carbon, nickel, titanium or silver on the surface thereof; analuminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; a conductive polymer; ametal paste comprising metal powders of Ni, Al, Au, Ag, Al, Pd/Ag, Cr,Ta, Cu, Ba or ITO; or a carbon paste comprising carbon powders ofgraphite, carbon black or carbon nanotube.

In the present invention, the core for supplying lithium ions comprisesan electrolyte, and examples of the electrolyte may include, but are notparticularly limited to, a non-aqueous electrolyte solution usingethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), vinylene carbonate (VC), diethyl carbonate (DEC), dimethylcarbonate (DMC), ethyl methyl carbonate (EMC), methyl formate (MF),γ-butyrolactone (γ-BL), sulfolane, methyl acetate (MA) or methylpropionate (MP); a gel polymer electrolyte using PEO, PVdF, PVdF-HEP,PMMA, PAN, or PVAc; and a solid electrolyte using PEO, polypropyleneoxide (PPO), polyether imine (PEI), polyethylene sulphide (PES), orpolyvinyl acetate (PVAc). The electrolyte further comprises a lithiumsalt, and the preferred examples of the lithium salt include LiCl, LiBr,LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆,LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate,lower aliphatic lithium carbonate, lithium tetraphenylborate, andmixtures thereof.

The first electrolyte-absorbing layer and the secondelectrolyte-absorbing layer are not particularly limited to their kinds,and may each independently comprise a polymer selected from a gelpolymer electrolyte using PEO, PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and asolid electrolyte using PEO, polypropylene oxide (PPO), polyether imine(PEI), polyethylene sulphide (PES), or polyvinyl acetate (PVAc). Also,these electrolyte-absorbing layers may further comprise a lithium salt.

In the present invention, the inner electrode may be an anode and theouter electrode may be a cathode, or the inner electrode may be acathode and the outer electrode may be an anode.

When the inner electrode of the present invention is an anode and theouter electrode is a cathode, the inner electrode active material layermay comprise an active material selected from the group consisting ofnatural graphite, artificial graphite, or carbonaceous material;lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn,Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; oxides (MeOx) ofthe metals; complexes of the metals and carbon; and mixtures thereof,and the outer electrode active material layer may comprise an activematerial selected from the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄,LiCoPO₄, LiFePO₄, LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂(wherein M1 and M2 are each independently selected from the groupconsisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, yand z are each independently an atomic fraction of oxide-formingelements, in which 0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1), and mixturesthereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material layer maycomprise an active material selected from the group consisting ofLiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof, and the outer electrodeactive material layer may comprise an active material selected from thegroup consisting of natural graphite, artificial graphite, orcarbonaceous material; lithium-titanium complex oxide (LTO), and metals(Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of themetals; oxides (MeOx) of the metals; complexes of the metals and carbon;and mixtures thereof, but the present invention is not particularlylimited thereto.

In the present invention, the separation layer may be an electrolytelayer or a separator.

The electrolyte layer is not particularly limited to its kinds, butpreferably is made of an electrolyte selected from a gel polymerelectrolyte using PEO, PVdF, PMMA, PAN, or PVAc; and a solid electrolyteof PEO, polypropylene oxide (PPO), polyether imine (PEI), polyethylenesulphide (PES), or polyvinyl acetate (PVAc). Also, the electrolyte layermay further comprise a lithium salt, and non-limiting examples of thelithium salt include LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆,LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithium carbonate,lithium tetraphenylborate, and mixtures thereof.

When the separation layer is a separator, the cable-type secondarybattery of the present invention needs an electrolyte solution, andexamples of the separator may include, but is not limited to, a poroussubstrate made of a polyolefin-based polymer selected from the groupconsisting of ethylene homopolymers, propylene homopolymers,ethylene-butene copolymers, ethylene-hexene copolymers, andethylene-methacrylate copolymers; a porous substrate made of a polymerselected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalenes; or a porous substrate made of a mixture ofinorganic particles and a binder polymer.

Further, the present invention provides a cable-type secondary batteryhaving multiple inner electrodes.

Advantageous Effects

In accordance with the present invention, a core for supplying lithiumions, which comprises an electrolyte, is disposed in the inner electrodehaving an open structure, from which the electrolyte of the core forsupplying lithium ions can be easily penetrated into an electrode activematerial, thereby facilitating the supply and exchange of lithium ions.Also, the inner electrode and the separation layer of the presentinvention have an electrolyte-absorbing layer on the outer surfacethereof, from which the electrolyte of the core for supplying lithiumions can be contained in the electrolyte-absorbing layer, therebyfacilitating the supply and exchange of lithium ions. Thus, thecable-type secondary battery of the present invention has such a corefor supplying lithium ions to exhibit superior capacity and cyclecharacteristics. Also, the cable-type secondary battery of the presentinvention has an inner electrode having an open structure to exhibitgood flexibility.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of thepresent invention and, together with the foregoing disclosure, serve toprovide further understanding of the technical spirit of the presentinvention. However, the present invention is not to be construed asbeing limited to the drawings.

FIG. 1 shows a cable-type secondary battery having one inner electrodein the form of a mesh together with a separation layer in accordancewith one embodiment of the present invention.

FIG. 2 shows a cable-type secondary battery having one inner electrodein the form of a wound wire together with a separation layer inaccordance with one embodiment of the present invention.

FIG. 3 is a cross-sectional view of a cable-type secondary batteryhaving multiple inner electrodes together with a separation layer inaccordance with one embodiment of the present invention.

BEST MODE

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings. Prior to the description, itshould be understood that the terms used in the specification and theappended claims should not be construed as limited to general anddictionary meanings, but interpreted based on the meanings and conceptscorresponding to technical aspects of the present invention on the basisof the principle that the inventor is allowed to define termsappropriately for the best explanation.

FIG. 1 schematically shows a cable-type secondary battery having oneinner electrode in the form of a mesh together with a separation layerin accordance with one embodiment of the present invention. However, theconfigurations illustrated in the drawings and the embodiments are justpreferable examples for the purpose of illustrations only, not intendedto limit the scope of the disclosure, so it should be understood thatother equivalents and modifications could be made thereto withoutdeparting from the spirit and scope of the disclosure.

Referring to FIG. 1, a cable-type secondary battery 100 having ahorizontal cross section of a predetermined shape and extendinglongitudinally comprises a core 110 for supplying lithium ions, whichcomprises an electrolyte; an inner electrode 120 comprising anopen-structured inner current collector surrounding the outer surface ofthe core for supplying lithium ions, an inner electrode active materiallayer formed on the surface of the inner current collector, and a firstelectrolyte-absorbing layer formed on the outer surface of the innerelectrode active material layer; a separation layer 130 surrounding theouter surface of the inner electrode to prevent a short circuit betweenelectrodes; a second electrolyte-absorbing layer 140 formed on thesurface of the separator; and an outer electrode surrounding the outersurface of the second electrolyte-absorbing layer and comprising anouter electrode active material layer and an outer current collector.

In the present invention, the outer electrode may be formed in variousembodiments depending on the disposition of the outer electrode activematerial layer and the outer current collector, which come into contactwith the second electrolyte-absorbing layer.

In FIG. 1, the outer electrode comprises an outer electrode activematerial layer 150 surrounding the outer surface of the secondelectrolyte-absorbing layer 140 and an outer current collector 160surrounding the outer surface of the outer electrode active materiallayer.

Also, the outer electrode of the cable-type secondary battery accordingto one embodiment of the present invention may be formed in a structurehaving the outer current collector formed to surround the outer surfaceof the second electrolyte-absorbing layer, and the outer electrodeactive material layer formed to surround the outer surface of the outercurrent collector; a structure having the outer current collector formedto surround the outer surface of the second electrolyte-absorbing layer,and the outer electrode active material layer formed to surround theouter surface of the outer current collector and to come into contactwith the second electrolyte-absorbing layer; or a structure having theouter electrode active material layer formed to surround the outersurface of the second electrolyte-absorbing layer, and the outer currentcollector formed to be included inside the outer electrode activematerial layer by being covered therein and to surround the outersurface of the second electrolyte-absorbing layer with spacing aparttherefrom.

The term ‘a predetermined shape’ used herein refers to not being limitedto any particular shape, and means that any shape that does not damagethe nature of the present invention is possible. The cable-typesecondary battery of the present invention has a horizontal crosssection of a predetermined shape, a linear structure, which extends inthe longitudinal direction, and flexibility, so it can freely change inshape. Also, the term ‘open-structured’ used herein means that astructure has an open boundary surface through which a substance may betransferred freely from the inside of the structure to the outsidethereof.

The conventional cable-type secondary batteries have an electrolytelayer which is interposed between an inner electrode and an outerelectrode. In order for the electrolyte layer to isolate the innerelectrode from the outer electrode and prevent a short circuit, it isrequired that the electrolyte layer be made of gel-type polymerelectrolytes or solid polymer electrolytes having a certain degree ofmechanical properties. However, such gel-type polymer electrolytes orsolid polymer electrolytes fail to provide superior performances as asource for lithium ions, so an electrolyte layer made of such shouldhave an increased thickness so as to sufficiently provide lithium ions.Such a thickness increase in the electrolyte layer widens an intervalbetween the electrodes to cause resistance increase, therebydeteriorating battery performances. In contrast, since the cable-typesecondary battery 100 of the present invention has the core 110 forsupplying lithium ions, which comprises an electrolyte, and the innercurrent collector of the present invention has an open structure, theelectrolyte of the core 110 for supplying lithium ions can pass throughthe inner current collector to reach the inner electrode active materiallayer and the outer electrode active material layer 150. Accordingly, itis not necessary to excessively increase the thickness of an electrolytelayer. Also, an electrolyte layer may not be adopted as an essentialcomponent, and therefore, only a separator may be optionally used. Thus,the cable-type secondary battery of the present invention has the core110 for supplying lithium ions, which comprises an electrolyte, tofacilitate the penetration of an electrolyte into an electrode activematerial, and eventually facilitate the supply and exchange of lithiumions in electrodes, thereby exhibiting superior capacity and cyclecharacteristics.

The inner electrode 120 of the present invention maintains its openstructure by forming the inner electrode active material layer by way ofcoating on the surface of the open-structured inner current collector,in which the first electrolyte-absorbing layer is also formed on thesurface of the inner electrode active material layer. The firstelectrolyte-absorbing layer may contain the electrolyte of the core 110for supplying lithium ions, and also comprise a lithium salt, tofacilitate the supply and exchange of lithium ions in electrodes,thereby providing superior capacity and cycle characteristics to thebattery. This inner electrode 120 has the open-structured inner currentcollector, which allows the penetration of the electrolyte comprised inthe core 110 for supplying lithium ions, and the open structure form maybe any form if it facilitates the penetration of the electrolyte.Referring to FIGS. 1 and 2, as a non-limiting example of theopen-structured inner current collector, an inner electrode 220 applyinga wound wire-type inner current collector, and an inner electrode 120applying a mesh-form inner current collector are illustrated.

The core 110 for supplying lithium ions comprises an electrolyte, andexamples of the electrolyte may include, but are not particularlylimited to, a non-aqueous electrolyte solution using ethylene carbonate(EC), propylene carbonate (PC), butylene carbonate (BC), vinylenecarbonate (VC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methyl formate (MF), γ-butyrolactone (γ-BL),sulfolane, methyl acetate (MA) or methyl propionate (MP); a gel polymerelectrolyte using PEO, PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and a solidelectrolyte using PEO, polypropylene oxide (PPO), polyether imine (PEI),polyethylene sulphide (PES), or polyvinyl acetate (PVAc). Theelectrolyte further comprises a lithium salt, and the preferred examplesof the lithium salt include LiCl, LiBr, LiI, LiClO₄, LiBF₁₀Cl₁₀, LiPF₆,LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithium carbonate,lithium tetraphenylborate, and the like. Also, the core 110 forsupplying lithium ions may consist of only an electrolyte, and in thecase of a liquid electrolyte, a porous carrier may be used together.

The inner current collector is preferably made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on the surface thereof;an aluminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; or a conductive polymer.

The current collector serves to collect electrons generated byelectrochemical reaction of the active material or to supply electronsrequired for the electrochemical reaction. In general, the currentcollector is made of a metal such as copper or aluminum. Especially,when the current collector is made of a non-conductive polymer treatedwith a conductive material on the surface thereof or a conductivepolymer, the current collector has a relatively higher flexibility thanthe current collector made of a metal such as copper or aluminum. Also,a polymer current collector may be used instead of the metal currentcollector to reduce the weight of the battery.

The conductive material may include polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, indium tin oxide (ITO),copper, silver, palladium, nickel, etc. The conductive polymer mayinclude polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, etc. However, the non-conductive polymer used for thecurrent collector is not particularly limited to its kinds.

In the present invention, the inner electrode active material layer isformed on the surface of the inner current collector which preferablymaintains an open structure form. On the surface of the inner electrodeactive material layer, the first electrolyte-absorbing layer is formed.The first electrolyte-absorbing layer may comprise a polymer selectedfrom a gel polymer electrolyte using PEO, PVdF, PVdF-HFP, PMMA, PAN, orPVAc; and a solid electrolyte using PEO, polypropylene oxide (PPO),polyether imine (PEI), polyethylene sulphide (PES), or polyvinyl acetate(PVAc), but is not particularly limited thereto. Also, theelectrolyte-absorbing layer may further comprise a lithium salt, and thepreferred examples of the lithium salt include LiCl, LiBr, LiI, LiClO₄,LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄,CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, lower aliphaticlithium carbonate, lithium tetraphenylborate, and the like.

In the present invention, the outer current collector is notparticularly limited to its forms, but is preferably in the form of apipe, a wound wire, a wound sheet or a mesh. The outer current collectormay be made of stainless steel, aluminum, nickel, titanium, sinteredcarbon, or copper; stainless steel treated with carbon, nickel, titaniumor silver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; a conductive polymer; a metal paste comprising metal powders ofNi, Al, Au, Ag, Al, Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon pastecomprising carbon powders of graphite, carbon black or carbon nanotube.

The inner electrode may be an anode and the outer electrode may be acathode. Alternatively, the inner electrode may be a cathode and theouter electrode may be an anode.

In the present invention, the electrode active material layer allowsions to move through the current collector, and the movement of ions iscaused by the interaction of ions such as intercalation/deintercalationof ions into and from the electrolyte layer.

Such an electrode active material layer may be divided into an anodeactive material layer and a cathode active material layer.

Specifically, when the inner electrode is an anode and the outerelectrode is a cathode, the inner electrode active material layerbecomes an anode active material layer and may be made of an activematerial selected from the group consisting of natural graphite,artificial graphite, or carbonaceous material; lithium-titanium complexoxide (LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Niand Fe; alloys of the metals; oxides (MeOx) of the metals; complexes ofthe metals and carbon; and mixtures thereof, and the outer electrodeactive material layer becomes a cathode active material layer and may bemade of an active material selected from the group consisting of LiCoO₂,LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material layer becomesa cathode active material layer and the outer electrode active materiallayer becomes an anode active material layer.

As mentioned above, referring to FIG. 1, the outer electrode comprisesan outer electrode active material layer 150 surrounding the outersurface of the separation layer 140 and an outer current collector 160surrounding the outer surface of the outer electrode active materiallayer 150.

Also, the outer electrode may have the outer current collector formed tosurround the outer surface of the second electrolyte-absorbing layer,and the outer electrode active material layer formed to surround theouter surface of the outer current collector; may have the outer currentcollector formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer electrode active materiallayer formed to surround the outer surface of the outer currentcollector and to come into contact with the second electrolyte-absorbinglayer; or may have the outer electrode active material layer formed tosurround the outer surface of the second electrolyte-absorbing layer,and the outer current collector formed to be included inside the outerelectrode active material layer by being covered therein and to surroundthe outer surface of the second electrolyte-absorbing layer with spacingapart therefrom.

Specifically, if the outer current collector is wound on the outersurface of the separation layer, a contact area of the secondelectrolyte-absorbing layer and the active material layer sufficientlyincreases to ensure a certain degree of battery performances.Particularly, since the outer electrode active material layer of thepresent invention is formed by coating an active material in the form ofa slurry on the outer surface of the outer current collector, the outerelectrode active material layer comes into contact with the secondelectrolyte-absorbing layer. Also, the outer current collector isincluded inside the outer electrode active material layer by beingcovered therein, while surrounding the outer surface of the secondelectrolyte-absorbing layer with spacing apart therefrom by the outerelectrode active material layer. As a result, an electric contactbetween the outer current collector and the outer electrode activematerial layer is improved, thereby contributing to the enhancement ofbattery characteristics.

For example, when the outer current collector is in the form of a woundwire having flexibility, the wound wire-form outer current collector haselasticity due to its form to enhance the overall flexibility of thecable-type secondary battery. Also, when excessive external force isapplied to the cable-type secondary battery of the present invention,the wire-form outer current collector of the present invention undergoesvery little excessive deformation such as crumpling or bending, so ashort circuit due to a contact with an inner current collector may beavoided.

The electrode active material layer comprises an electrode activematerial, a binder and a conductive material, and is combined with acurrent collector to configure an electrode. If the electrode isdeformed by bending or severely folding due to external force, theelectrode active material may be released. The release of the electrodeactive material deteriorates the performance and capacity of batteries.However, in accordance with the present invention, the wound wire-formouter current collector having elasticity functions to disperse theapplied force when such a deformation occurs by the external force, fromwhich the active material layer is less deformed, thereby preventing therelease of the active material.

The separation layer of the present invention may be an electrolytelayer or a separator. On the outer surface of the separation layer, thesecond electrolyte-absorbing layer is formed, and the secondelectrolyte-absorbing layer can contain the electrolyte of the core 110for supplying lithium ions and a lithium salt to facilitate the supplyand exchange of lithium ions in electrodes, thereby contributing toimprove the capacity and cycle characteristics of a battery. Such asecond electrolyte-absorbing layer may comprise, but is not particularlylimited to, a polymer selected from a gel polymer electrolyte using PEO,PVdF, PVdF-HFP, PMMA, PAN, or PVAc; and a solid electrolyte using PEO,polypropylene oxide (PPO), polyether imine (PEI), polyethylene sulphide(PES), or polyvinyl acetate (PVAc). Also, the electrolyte-absorbinglayer may further comprise a lithium salt, and the preferred examples ofthe lithium salt include LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀CL₁₀,LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithium carbonate,lithium tetraphenylborate, and the like.

The electrolyte layer, which is used as the separation layer to serve asan ion channel, may be made of a gel-type polymer electrolyte using PEO,PVdF, PVdF-HFP, PMMA, PAN or PVAC, or a solid electrolyte using PEO,polypropylene oxide (PPO), polyethylene imine (PEI), polyethylenesulfide (PES) or polyvinyl acetate (PVAc). The matrix of the solidelectrolyte is preferably formed using a polymer or a ceramic glass asthe backbone. In the case of typical polymer electrolytes, the ions movevery slowly in terms of reaction rate, even when the ionic conductivityis satisfied. Thus, the gel-type polymer electrolyte which facilitatesthe movement of ions is preferably used compared to the solidelectrolyte. The gel-type polymer electrolyte has poor mechanicalproperties and thus may comprise a porous support or a cross-linkedpolymer to improve poor mechanical properties. The electrolyte layer ofthe present invention can serve as a separator, and thus an additionalseparator may be omitted. The electrolyte layer of the present inventionmay further comprise a lithium salt.

The lithium salt can improve an ionic conductivity and response time.Non-limiting examples of the lithium salt may include LiCl, LiBr, LiI,LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆,LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, loweraliphatic lithium carbonate, and lithium tetraphenylborate.

Examples of the separator may include, but is not limited to, a poroussubstrate made of a polyolefin-based polymer selected from the groupconsisting of ethylene homopolymers, propylene homopolymers,ethylene-butene copolymers, ethylene-hexene copolymers, andethylene-methacrylate copolymers; a porous substrate made of a polymerselected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalenes; or a porous substrate made of a mixture ofinorganic particles and a binder polymer. Among these, in order for thelithium ions of the core for supplying lithium ions to be transferred tothe outer electrode, it is preferred to use a non-woven fabric separatorcorresponding to the porous substrate made of a polymer selected fromthe group consisting of polyesters, polyacetals, polyamides,polycarbonates, polyimides, polyether ether ketones, polyether sulfones,polyphenylene oxides, polyphenylene sulfides and polyethylenenaphthalenes.

Also, the cable-type secondary battery of the present invention has aprotection coating. The protection coating is an insulator and is formedto surround the outer current collector, thereby protecting theelectrodes against moisture in the air and external impacts. Theprotection coating may be made of conventional polymer resins, forexample, PVC, HDPE or epoxy resins.

Hereinafter, a cable-type secondary battery according to one embodimentof the present invention and the manufacture thereof will be brieflyexplained with reference to FIG. 1.

A cable-type secondary battery 100 according to one embodiment of thepresent invention comprises a core 110 for supplying lithium ions, whichcomprises an electrolyte; an inner electrode 120 comprising a mesh-forminner current collector surrounding the outer surface of the core forsupplying lithium ions, an inner electrode active material layer formedon the surface of the inner current collector, and a firstelectrolyte-absorbing layer formed on the outer surface of the innerelectrode active material layer; a separation layer 130 surrounding theouter surface of the inner electrode to prevent a short circuit betweenelectrodes; a second electrolyte-absorbing layer 140 formed on thesurface of the separator; and an outer electrode having an outer activematerial layer 150 surrounding the outer surface of the secondelectrolyte-absorbing layer and an outer current collector 160surrounding the outer surface of the outer electrode active materiallayer 150.

First, a polymer electrolyte is provided in the form of a wire using anextruder to prepare the core 110 for supplying lithium ions. Also, thecore 110 for supplying lithium ions may be formed by providing a hollowinner electrode and introducing a non-aqueous electrolyte solution inthe center of the inner electrode, or may be formed by providing abattery assembly comprising a protection coating as well as the othersand introducing a non-aqueous electrolyte solution in the center of theinner electrode support comprised in the battery assembly.Alternatively, the core 110 for supplying lithium ions may be preparedby providing a wire-form carrier made of a sponge material andintroducing a non-aqueous electrolyte solution thereto.

Then, after providing a mesh-form inner current collector, on thesurface of the mesh-form inner current collector, an inner electrodeactive material layer is formed by way of coating. The coating may becarried out by various conventional methods, for example, by anelectroplating process or an anodic oxidation process. Also, in order tomaintain constant intervals, an electrode slurry containing an activematerial may be discontinuously applied by way of an extrusion-coatingusing an extruder. In addition, the electrode slurry containing anactive material may be applied by way of dip coating orextrusion-coating using an extruder.

On the surface of the inner electrode active material layer formed bycoating, a first electrolyte-absorbing layer is formed to obtain theinner electrode 120. The formation of the first electrolyte-absorbinglayer may be carried out by way of dip coating or extrusion-coatingusing an extruder. The inner electrode 120 thus obtained is formed onthe outer surface of the core 110 for supplying lithium ions.

Subsequently, the separation layer 130 made of a non-woven fabric isformed to surround the inner electrode 120.

Next, on the outer surface of the separation layer 130, the secondelectrolyte-absorbing layer 140 is formed. Alternatively, the secondelectrolyte-absorbing layer 140 which is pre-formed on the surface ofthe non-woven fabric may be formed to surround the inner electrode 120.

On the outer surface of the second electrolyte-absorbing layer 140, theouter electrode active material layer 150 is formed by way of coating.The coating method of the inner electrode active material layer may beidentically applied to the formation of the outer electrode activematerial layer 150.

Then, an outer current collector in the form of a wire is provided andwound on the outer surface of the outer electrode active material layer150 to form the wound wire-form outer current collector 160. In thepresent invention, as the outer current collector, a wound sheet-, pipe-or mesh-form current collector may be used.

At this time, the outer electrode active material layer may be firstformed on the outer current collector and then the secondelectrolyte-absorbing layer is applied thereon, to form the outerelectrode. For example, in the case of the wound sheet-form currentcollector, the outer electrode active material layer may be first formedon the wound sheet-form current collector, followed by cutting into apiece having a predetermined size, to prepare a sheet-form outerelectrode. Then, the prepared sheet-form outer electrode may be wound onthe outer surface of the second electrolyte-absorbing layer so that theouter electrode active material layer comes into contact with the secondelectrolyte-absorbing layer, to form the outer electrode on the secondelectrolyte-absorbing layer.

As another method, in the formation of the outer electrode, the outercurrent collector may be first formed to surround the outer surface ofthe second electrolyte-absorbing layer, followed by forming the outerelectrode active material layer to surround the outer surface of theouter current collector.

Meanwhile, in the case of a structure having the outer current collectorformed to surround the outer surface of the second electrolyte-absorbinglayer, and the outer electrode active material layer formed to surroundthe outer surface of the outer current collector and to come intocontact with the second electrolyte-absorbing layer, first, an outercurrent collector, for example, in the form of a wire or sheet, is woundon the outer surface of the second electrolyte-absorbing layer. Thewinding method is not particularly limited. For example, in the case ofthe wire-form current collector, the winding may be carried out by usinga winding machine on the outer surface of the secondelectrolyte-absorbing layer. Then, the outer electrode active materiallayer is formed by way of coating on the outer surface of the woundwire- or sheet-form outer current collector so that the outer electrodeactive material layer surrounds the outer current collector and comesinto contact with the second electrolyte-absorbing layer.

Also, in the case of a structure having the outer electrode activematerial layer formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer current collector formed tobe included inside the outer electrode active material layer by beingcovered therein and to surround the outer surface of the secondelectrolyte-absorbing layer with spacing apart therefrom, first, on theouter surface of the second electrolyte-absorbing layer, a part of theouter electrode active material layer to be finally obtained is formed,on which the outer current collector is formed to surround the part ofthe outer electrode active material layer, and then the outer electrodeactive material layer is further formed on the outer current collectorto completely cover the outer current collector. Thereby, the outercurrent collector is disposed inside the outer electrode active materiallayer with spacing apart from the second electrolyte-absorbing layer, toimprove an electric contact between the current collector and the activematerial, thereby enhancing battery characteristics. Finally, theprotection coating 170 is formed to surround the outer surface of theelectrode assembly. The protection coating 170 is an insulator and isformed on the outermost surface for the purpose of protecting theelectrodes against moisture in the air and external impacts. As theprotection coating 170, conventional polymer resins, for example, PVC,HDPE and epoxy resins may be used.

Hereinafter, another embodiment of the present invention will be brieflyexplained with reference to FIGS. 2 and 3.

Referring to FIG. 2, a cable-type secondary battery 200 according to oneembodiment of the present invention comprises a core 210 for supplyinglithium ions, which comprises an electrolyte; an inner electrode 220comprising a wound wire-form inner current collector surrounding theouter surface of the core for supplying lithium ions, an inner electrodeactive material layer formed on the surface of the inner currentcollector, and a first electrolyte-absorbing layer formed on the outersurface of the inner electrode active material layer; a separation layer230 surrounding the outer surface of the inner electrode to prevent ashort circuit between electrodes; a second electrolyte-absorbing layer240 formed on the surface of the separator; and an outer electrodehaving an outer active material layer 250 surrounding the outer surfaceof the second electrolyte-absorbing layer and an outer current collector260 surrounding the outer surface of the outer electrode active materiallayer 250.

Referring to FIG. 3, a cable-type secondary battery 300 according to oneembodiment of the present invention comprises two or more cores 310 forsupplying lithium ions, which comprise an electrolyte; two or more innerelectrodes 320 arranged parallel to each other, each inner electrodesurrounding the outer surface of each core for supplying lithium ions,and comprising an open-structured inner current collector to surroundthe outer surface of each core 310 for supplying lithium ions, an innerelectrode active material layer formed on the surface of the innercurrent collector, and a first electrolyte-absorbing layer formed on theouter surface of the inner electrode active material layer; a separationlayer 330 surrounding the outer surface of the inner electrode 320 toprevent a short circuit between electrodes; a secondelectrolyte-absorbing layer 340 formed on the surface of the separator330; and an outer electrode having an outer active material layer 350surrounding the outer surface of the second electrolyte-absorbing layer340 and an outer current collector 360 surrounding the outer surface ofthe outer electrode active material layer 350. Such a cable-typesecondary battery 300 has the inner electrode consisting of multipleelectrodes, thereby allowing controlling the balance between a cathodeand anode and preventing a short circuit.

Also, in these cable-type secondary batteries having one wound wire-forminner electrode together with a separator (FIG. 2), or multiple innerelectrodes together with a separator (FIG. 3), besides the structure ofthe outer electrode having the outer electrode active material layerformed to surround the outer surface of the second electrolyte-absorbinglayer, and the outer current collector formed to surround the outersurface of the outer electrode active material layer, as mentionedabove, the outer electrode may be formed in a structure having the outercurrent collector formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer electrode active materiallayer formed to surround the outer surface of the outer currentcollector; a structure having the outer current collector formed tosurround the outer surface of the second electrolyte-absorbing layer,and the outer electrode active material layer formed to surround theouter surface of the outer current collector and to come into contactwith the second electrolyte-absorbing layer; or a structure having theouter electrode active material layer formed to surround the outersurface of the second electrolyte-absorbing layer, and the outer currentcollector formed to be included inside the outer electrode activematerial layer by being covered therein and to surround the outersurface of the second electrolyte-absorbing layer with spacing aparttherefrom.

EXPLANATION OF REFERENCE NUMERALS

-   100, 200, 300: Cable-type Secondary Battery-   110, 210, 310: Core for Supplying Lithium Ions-   120, 220, 320: Inner Electrode-   130, 230, 330: Separation Layer-   140, 240, 340: Second Electrolyte-Absorbing Layer-   150, 250, 350: Outer Electrode Active Material Layer-   160, 260, 360: Outer Current Collector-   170, 270, 370: Protection Coating

What is claimed is:
 1. A cable-type secondary battery comprising: a coreincluding an electrolyte for supplying lithium ions; an inner electrode,comprising an open-structured inner current collector surrounding anouter surface of the core for supplying lithium ions, an inner electrodeactive material layer formed on a surface of the inner currentcollector, and a first electrolyte-absorbing layer formed on an outersurface of the inner electrode active material layer; a separation layersurrounding an outer surface of the inner electrode to prevent a shortcircuit between electrodes; a second electrolyte-absorbing layer formedon a surface of the separation layer; and an outer electrode surroundingan outer surface of the second electrolyte-absorbing layer andcomprising an outer electrode active material layer and an outer currentcollector.
 2. The cable-type secondary battery according to claim 1,wherein the open-structured inner current collector is in the form of awound wire or a mesh.
 3. The cable-type secondary battery according toclaim 1, wherein in the outer electrode, the outer electrode activematerial layer is formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer current collector is formedto surround the outer surface of an outer electrode active materiallayer; the outer current collector is formed to surround the outersurface of the second electrolyte-absorbing layer, and the outerelectrode active material layer is formed to surround an outer surfaceof the outer current collector; the outer current collector is formed tosurround the outer surface of the second electrolyte-absorbing layer,and the outer electrode active material layer is formed to surround theouter surface of the outer current collector and come into contact withthe second electrolyte-absorbing layer; or the outer electrode activematerial layer is formed to surround the outer surface of the secondelectrolyte-absorbing layer, and the outer current collector is formedto be included inside the outer electrode active material layer by beingcovered therein and to surround the outer surface of the secondelectrolyte-absorbing layer with spacing apart therefrom.
 4. Thecable-type secondary battery according to claim 1, wherein the outercurrent collector is in the form of a pipe, a wound wire, a wound sheetor a mesh.
 5. The cable-type secondary battery according to claim 1,wherein the inner current collector is made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on a surface thereof; analuminum-cadmium alloy; a non-conductive polymer treated with aconductive material on a surface thereof; or a conductive polymer. 6.The cable-type secondary battery according to claim 5, wherein theconductive material is selected from the group consisting ofpolyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, indium tin oxide (ITO), silver, palladium, nickel,and mixtures thereof.
 7. The cable-type secondary battery according toclaim 5, wherein the conductive polymer is selected from the groupconsisting of polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, and mixtures thereof.
 8. The cable-type secondarybattery according to claim 1, wherein the outer current collector ismade of stainless steel, aluminum, nickel, titanium, sintered carbon, orcopper; stainless steel treated with carbon, nickel, titanium or silveron a surface thereof; an aluminum-cadmium alloy; a non-conductivepolymer treated with a conductive material on a surface thereof; aconductive polymer; a metal paste comprising metal powders of Ni, Al,Au, Ag, Al, Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon paste comprisingcarbon powders of graphite, carbon black or carbon nanotube.
 9. Thecable-type secondary battery according to claim 1, wherein theelectrolyte comprises an electrolyte selected from a non-aqueouselectrolyte solution using ethylene carbonate (EC), propylene carbonate(PC), butylene carbonate (BC), vinylene carbonate (VC), diethylcarbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC),methyl formate (MF), γ-butyrolactone (γ-BL), sulfolane, methyl acetate(MA) or methyl propionate (MP); a gel polymer electrolyte using PEO,PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and a solid electrolyte using PEO,polypropylene oxide (PPO), polyether imine (PEI), polyethylene sulphide(PES), or polyvinyl acetate (PVAc).
 10. The cable-type secondary batteryaccording to claim 1, wherein the electrolyte further comprises alithium salt.
 11. The cable-type secondary battery according to claim10, wherein the lithium salt is selected from the group consisting ofLiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiShF₆, LiAlCl₄, CH₃SO₃L₁, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithiumchloroborate, lower aliphatic lithium carbonate, lithiumtetraphenylborate, and mixtures thereof.
 12. The cable-type secondarybattery according to claim 1, wherein the inner electrode is an anodeand the outer electrode is a cathode, or the inner electrode is acathode and the outer electrode is an anode.
 13. The cable-typesecondary battery according to claim 1, wherein when the inner electrodeis an anode and the outer electrode is a cathode, the inner electrodeactive material layer comprises an active material selected from thegroup consisting of natural graphite, artificial graphite, orcarbonaceous material; lithium-titanium complex oxide (LTO), and metals(Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of themetals; oxides (MeOx) of the metals; complexes of the metals and carbon;and mixtures thereof, and the outer electrode active material layercomprises an active material selected from the group consisting ofLiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)CO_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof.
 14. The cable-typesecondary battery according to claim 1, wherein the firstelectrolyte-absorbing layer and the second electrolyte-absorbing layereach independently comprise a polymer selected from a gel polymerelectrolyte using PEO, PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and a solidelectrolyte using PEO, polypropylene oxide (PPO), polyether imine (PEI),polyethylene sulphide (PES), or polyvinyl acetate (PVAc).
 15. Thecable-type secondary battery according to claim 1, wherein the firstelectrolyte-absorbing layer and the second electrolyte-absorbing layereach independently further comprise a lithium salt.
 16. The cable-typesecondary battery according to claim 15, wherein the lithium salt isselected from the group consisting of LiCl, LiBr, LiI, LiClO₄, LiBF₄,LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiShF₆, LiAlCl₄, CH₃SO₃L₁,CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithiumcarbonate, lithium tetraphenylborate, and mixtures thereof.
 17. Thecable-type secondary battery according to claim 1, wherein when theinner electrode is a cathode and the outer electrode is an anode, theinner electrode active material layer comprises an active materialselected from the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄,LiFePO₄, LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 andM2 are each independently selected from the group consisting of Al, Ni,Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are eachindependently an atomic fraction of oxide-forming elements, in which0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1) and mixtures thereof, and theouter electrode active material layer comprises an active materialselected from the group consisting of natural graphite, artificialgraphite, or carbonaceous material; lithium-titanium complex oxide(LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe;alloys of the metals; oxides (MeOx) of the metals; complexes of themetals and carbon; and mixtures thereof.
 18. The cable-type secondarybattery according to claim 1, wherein the separation layer is anelectrolyte layer or a separator.
 19. The cable-type secondary batteryaccording to claim 18, wherein the electrolyte layer comprises anelectrolyte selected from a gel polymer electrolyte using PEO, PVdF,PMMA, PAN, or PVAc; and a solid electrolyte using PEO, polypropyleneoxide (PPO), polyether imine (PEI), polyethylene sulphide (PES), orpolyvinyl acetate (PVAc).
 20. The cable-type secondary battery accordingto claim 19, wherein the electrolyte layer further comprises a lithiumsalt.
 21. The cable-type secondary battery according to claim 20,wherein the lithium salt is selected from the group consisting of LiCl,LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆,LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate,lower aliphatic lithium carbonate, lithium tetraphenylborate, andmixtures thereof.
 22. The cable-type secondary battery according toclaim 18, wherein the separator is a porous substrate made of apolyolefin-based polymer selected from the group consisting of ethylenehomopolymers, propylene homopolymers, ethylene-butene copolymers,ethylene-hexene copolymers, and ethylene-methacrylate copolymers; aporous substrate made of a polymer selected from the group consisting ofpolyesters, polyacetals, polyamides, polycarbonates, polyimides,polyether ether ketones, polyether sulfones, polyphenylene oxides,polyphenylene sulfides and polyethylene naphthalenes; or a poroussubstrate made of a mixture of inorganic particles and a binder polymer.23. A cable-type secondary battery comprising: two or more cores eachincluding an electrolyte and for supplying lithium ions; two or moreinner electrodes arranged in parallel to each other, each innerelectrode comprising an open-structured inner current collectorsurrounding an outer surface of a core of the two or more cores forsupplying lithium ions, an inner electrode active material layer formedon a surface of the inner current collector, and a firstelectrolyte-absorbing layer formed on an outer surface of the innerelectrode active material layer; a separation layer surroundingrespective outer surfaces of the two or more inner electrodes to preventa short circuit between electrodes; a second electrolyte-absorbing layerformed on an outer surface of the separation layer; and an outerelectrode surrounding an outer surface of the secondelectrolyte-absorbing layer and comprising an outer electrode activematerial layer and an outer current collector.